Muscles control every bodily movement by electrical impulses created by the brain and relayed through the nerves. There are three types of muscles:
Muscles control every bodily movement by electrical impulses created by the brain and relayed through the nerves. There are three types of muscles:
| Skeletal | The skeletal muscles are voluntary, meaning that their movement can be controlled, and are attached to bones or other muscles. Skeletal muscles are the muscles that help you raise your hand, swim, ride a bike, or turn your head. |
| Smooth | The smooth muscles are involuntary, meaning that they control movements that are necessary for normal living, such as breathing and blinking. They control the functions of the organs. |
| Cardiac | The cardiac muscle is the muscle which regulates the blood flow and rate at which blood is pumped through the heart. This muscle is involuntary. |
MUSCLES WORK IN PAIRS!
The prime mover or agonist causes the primary motion or action while the antagonist provides an opposing force to dampen and help control the 1st degree movement. WIthout the antagonist, the prime mover would have nothing preventing it from overextension or flexion. The synergist helps the prime mover (2nd degree movement).
Did you ever wonder what the technical term for raising you hand was?
| Flexion | A
motion whcih decreases the angle between two body parts.
EX: pulling your hand to your shoulder, pulling your knee to your backside
|
| Extension | A
motion that increases the angle between two body parts (the opposite of
flexion).
EX: straightening your arm or leg
|
| Abduction | Moving
a body part away from the trunk or mid-line.
EX: moving your arm away from your body (sideways), moving your leg laterally from your other leg
|
| Adduction | Moving
a body part towards the mid-line (the opposite of abduction).
EX: pulling your arm towards your body, pulling your leg towards your other leg
|
| Circumduction | Moving
a body part so that it follows a circle
EX: moving the entire arm, without rotating it, so that the hand moves in a big circle
|
| Rotation | "twirling"
a body part around its axis
EX: twisting the wrist so that the hand makes a circular motion (turning a doorknob) |
Raising
your hand is an extension of the arm (as long as the elbow is straight)
and an abduction of the arm because the arm is moving away from the body.
Q. How do your muscles know when to move?
A. The Sliding Filament Theory
| The
blue and purple lines are actin (a protein), the red bands are myosin (another
protein)
|
| The
myosin have crossbridges which attach to actin and make the muscle contract.
|
| The
crossbridges attach to active sites on the actin, then the crossbridges
'flip' to draw the actin together.
|
| Once
the crossbridges have flipped, they attach to another active site that
is farther along the actin protein.
|
| This flipping continues until the myosin is left with no active sites on the actin, thus the muscle reaches its contracting capabilities. |
Now, the tricky part: when a muscle is told to contract.
| Under normal conditions, when a muscle is relaxed, a protein called tropomyosin covers the active sites so that the crossbridges cannot keep flipping to contract the muscle. |
| The brain releases its 'command' for a muscle to contract through a neurotransmittor called acetylcholine which causes an electrical impulse |
| When the electrical impulse reaches the muscle cell and the endoplasmic reticulum (in a muscle cell, the ER is called a sarcoplasmic reticulum) calcium ions are released. |
| These calcium ions stick to the protein troponin to pull the tropomyosin out of the active site. This allows the crossbridges to attach to the actin, and the muscle to contract. |
Now you have it, the essential facts as to how your muscles control your movements.
For more on this
subject, you can talk to the best anatomy teacher, Mr.Arbo,
or you can even
email him here!
References:
Oxford Encyclopedia of Science. http://www.oup.co.uk/oxed/children/yoes/ pictures/humans/muscles/
Life Science Connections. http://vilenski.org/science/humanbody/ hb_html/muscles.html
University of Colorado. http://biology.clc.uc.edu/courses/ bio105/muscles.htm
Link Publishing, Interactive Exams. http://www.linkpublishing.com/cgi-bin/ ie.cgi?exam=chap19p2.exm
Weight Trainer.Com. http://www.weightrainer.com/physiology/
muscle1.html
Created By: Megan Hamilton